Pull the TB off, on the bottom you have whats called a fast idle valve.. Remove the cover and see if the plunger is broke, or loose! If loose then tighten it up with a flat head, if broke, then replace it..

if your lost, then get some real help.. Its easy to check, just not easy with TB still in on the intake in the car..

p.s

Look for the small coolant hoses running into the TB, that is what you need to get off..


Edit: other checks consist of checking for vaccum leaks on the intake, TB.. (carb cleaner works great) spray and listen for engine to change tone!

remember I have no idea what you have done to the car before, I can only give my advise!